The invention relates generally to product coding and marking operations, and more particularly to systems and methods for controlling ribbon tension in printer systems useable for transferring print from a ribbon onto a substrate.
In many printing systems an inked ribbon or foil is supplied from an unwind reel, between a print head and a substrate and then to a rewind reel. The ribbon is usually drawn under tension from the unwind reel by the rewind reel or by a ribbon feed roller. The ribbon is often advanced intermittently during or between printing operations, wherein the print head is actuatable, either rotationally or relatively linearly, to transfer ink from the ribbon onto a target area of the substrate. These types of printing systems include, for example, thermal printers and hot stamp imprinters useable for printing variable information on products and packaging in coding and marking operations.
In printing systems where the ribbon is drawn from an unwind reel, it is known generally to control tension on the ribbon with a pivotal dancer arm having a dancer ribbon guide about which the ribbon is disposed. As ribbon is drawn from the unwind reel, the dancer arm pivots to maintain relatively constant tension thereon, and more particularly the dancer arm compensates for the inability of the unwind reel to change its angular velocity relatively instantaneously in response to changing demand for ribbon, resulting from the relatively large moment of inertia of the unwind reel.
In some applications the dancer arm does not compensate fully for the relatively large moment of inertia of the unwind reel, particularly in applications where the ribbon is accelerated and decelerated relatively rapidly. More particularly, tension in the ribbon may become excessive during ribbon acceleration, resulting possibly in breakage thereof. Additionally, the ribbon may become excessively slack during ribbon deceleration, which is also undesirable. These adverse effects are especially problematic in intermittent ribbon drawing applications where the ribbon is advanced and stopped relatively frequently, referred to herein as rapid cycling, which is typical in high production coding and marking operations.
It is also known generally to indicate when ribbon supplied from the unwind reel has become depleted. Europoean Patent Publication No. EP 0,683,055 entitled "Economic Use of Impression Transfer Material Printing Method" published Nov. 22, 1995 in the name of Prestek Limited, for example, discloses an electronic sensor located along the ribbon supply path for signalling lack of ribbon and for disabling the printing apparatus in response thereto.
The present invention is drawn toward advancements in the art of controlling ribbon tension and braking rotation of a ribbon unwind reel in printer systems useable for transferring print from a ribbon onto a substrate, particularly in coding and marking operations.
It is thus an object of the invention to provide novel methods and systems for controlling ribbon tension that overcomes problems in the prior art.
It is a more particular object of the invention to provide novel methods and systems for controlling ribbon tension in printer system useable for transferring print from a ribbon supplied from a ribbon supply roll disposed on a rotatable unwind reel with a pivotal dancer arm. And it is a related object of the invention to bias a pivotal brake member toward and into engagement with the unwind reel to brake rotation of the unwind reel to stem the supply of ribbon therefrom when drawing tension on the ribbon decreases to a first tension, whereby the dancer arm is engageable with the brake member to pivot the brake member away from the unwind reel to supply ribbon therefrom when the drawing tension increases.
It is another object of the invention to provide novel methods and systems for controlling ribbon tension in printer systems and indicating ribbon breakage or ribbon depletion by actuating a sensor with the dancer arm when the ribbon tension is reduced to a second tension less than the first tension.
These and other objects, aspects, features and advantages of the present invention will become more fully apparent upon careful consideration of the following Detailed Description of the Invention and the accompanying Drawings, which may be disproportionate for ease of understanding, wherein like structure and steps are referenced generally by corresponding numerals and indicators.